Lubricant



Patented Nov. 8, 1949 ATENT OFFICE 2,487,379 LUBRICANT Theodore G. Roehner, Mount Vernon, and George W. Murray, Pleasantville, N. Y., assignors to Socony-Vacuum Oil Company,

Incorporated,

a corporation of New York No Drawing. Application April 17, 1948, Serial No. 21,758

Claims. (Cl. 25.2-40.5)

This invention relates to lubricants and, more particularly, is concerned with lubricants characterized by a high order of effectiveness under severe operating conditions.

It is well known that lubricants generally lose some or all of their effectiveness when subjected to high temperature and pressure conditions, and this is particularly true of greases exposed to such conditions. In lubricating machine parts with a grease, it is essential to provide a grease which will substantially retain its character under the foregoing conditions. Failure to do so results in high consumption of the lubricant and frequent servicing. 'In general, available greases suffer from a marked tendency to change in character when used over a wide range of temperature. For example, the consistency of a conventional grease is prone to change over a wide range of temperature. Certain soda base greases, for example, have a pronounced and undesirable property of changing from a short to a lon fibre structure with temperature change. Some conventional greases are also characterized by excessive softening when exposed to elevated temperatures, thereby being extruded too rapidly from the area being lubricated to provide efficient lubrication. In addition, some greases tend to lose their oil content when used at elevated temperatures and pressures. This condition is generally referred to in the art as bleeding.

In accordance with the present invention, there has now been discovered a grease which is characterized by a high order of effectiveness under severe operating conditions and which is substantially free from the shortcomings discussed above. The greases contemplated herein contain, as a characterizing or reinforcing agent, a small amount of a water-dispersible or oil-insoluble and water-soluble natural Representative of the natural gums contemplated as reinforcing agents in the greases of this invention, are gum arabic, gum tra'gacanth, and gum karaya. While the use of one or more of the above natural gums represents a preferred embodiment of the invention, it is likewise contemplated that other water-dispersible natural gums known in the art may be employed in improving the heat-resistant characteristics of the greases described herein.

The greases of this invention containing one or more of the aforesaid characterizing agents are the alkali metal and alkaline earth metal base greases; that is, those grease compositions consisting of mineral oil in admixture with alkali metal or alkaline earth metal soaps of fatty acids or with a sufficient proportion of such soaps present to give the characteristics usually recognized as attributable to alkali and alkaline earth metal base greases. The soap content of these greases is generally between about 10 and about 55 per cent :by weight on the basis of the final product. They are generally prepared by heating a fat or a fatty acid, or a mixture thereof, with a mineral oil and thereafter heating the resultant mixture with the desired metal hydroxide at elevated temperatures to obtain a substantially anhydrous metal base grease. The final product so obtained generally contains 8.5 to 48 per cent fat or fatty acid; 1.5 to 7.5 per cent metal hydroxide (dry basis); and 29.5 to 89.5 per cent mineral oil. In obtaining the grease, the mixture may be cooked, for example, at temperatures of 250 to 400 F. Available steam-cooked greases do not maintain their shape :at elevated temperatures and firecooked greases are typified by bleeding under such conditions.

The mineral oil constituent of the greases contemplated herein may vary considerably in character and includes residual or distilled oils. Preference is accorded, however, to oils having a viscosity (S. U. V.) of 100 to 250 seconds at 210 F. Similarly, the fats and fatty acids which may be used are those generally found in the soap type greases. Representative of such materials are vegetable, animal, and fish fatty oils, and hydrogenated fatty materials thereof. While sodium hydroxide and calcium hydroxide are preferred in view of cost considerations and a greater de mand by industry for soda and lime base greases,

other metal hydroxides may be used in the present greases, preferably where the soa constituent of the grease is prepared by direct saponification in aqueous phase. Accordingly, such other metal hydroxides as those of lithium, potassium, magnesium, barium, strontium, etc., are contemplated herein, with the alkali metal hydroxides preferred.

It has been found, in accordance with this invention, that from one to two parts by weight of alkali or alkaline earth metal soap may be replaced with one part of water-dispersible natural gum to yield a resulting lubricating grease composition characterized by resistance to deformation, and bleeding. 'The particular degree of substitution of soap by the water-dispersible natural gum will depend in part on the nature of the soap being replaced. Thus, in the case of a sodium base grease, approximately one part by weight of water-dispersible natural gum will replace one and one-half parts by Weight of soap,

while with a calcium base grease, approximately one part by weight of natural gum may be substituted for two parts by weight ofjsoap. Likewise, the extent of substitution of soap by water-dis- 3 persible natural gum depends on the nature of the soap being replaced. It is generally contemplated, however, that the replacement of soap by natural gum will not exceed about 30 per cent of the soap content. Thus, in the case of a soda base grease, it has been found that up to 30 per cent of the soap could be replaced with water-dispersible natural gum. For example, 50 per cent soap in a soda base grease may be replaced with 35 per cent soap and 15 per cent of water-dispersible natural gum. In the case of a lime base. grease, up to 20 per cent of the soap may be replaced with water-dispersible natural gum. For instance, 50 per cent soap content in a lime basegrease may be replaced with 40 per centpf the same soap and per cent of water-dispersible natural gum.

It will thus be apparent that the characterizing materials of this invention may be used in various amounts extending over a range of from about per cent to about per cent. Preferred amounts for the alkali metal greases, such as soda base grease, are of the order of per cent to 6 per cent and for the alkaline earth metal greases, typified by lime base grease, are from about per cent to about 4 per cent by weight of the finished grease.

It has further been discovered that the characterizing water-dispersible natural gums described above are most advantageously incorporated in the soap greases prior to or during the saponification stage, as illustrated by the following procedure. A fat or fatty acid, or mixture thereof, is added to mineral oil in order to provide a blend thereof; if necessary, the materials may be heated in order to thoroughly distribute the fatty material in the mineral oil. The characterizing material of water-soluble or water-dispersible natural gum is then dissolved or dispersed in water and the resulting water solution is dispersed or emulsified with the blend of fatty material and mineral oil. The resulting dispersion or emulsion is thereafter saponified with a metal hydroxide solution such as caustic soda. Following the latter treatment, water-of solution and of reaction-is evaporated by heating and stirring the saponified mixture at a temperature above about 220 F, preferably at 260 F. In this evaporation operation, the saponified mixture may also be steam-cooked at temperatures of the order of 250 to 330 F. or fire-cooked at temperatures in the range of 300 to 450 F. The grease is then withdrawn from the vessel in which it was prepared and run into a suitable mold. The grease is allowed to cool, whereupon it solidifies. The solid grease may then be cut into cakes of desired size. By following this preferred procedure, the characterizing water-dispersible natural gum is incorporated in the grease in an extremely fine dispersed state and the grease is provided with a high order of eifectiveness. V

The greases of this invention are illustrated by the following typical example:

Example ring in 50 parts of cold water. Forty-four parts of mineral oil (S. U. V. of seconds at 210 F.) and 30 parts of a fatty material were then added with stirring to the gum arabic solution and heated. The fatty material was amixture of hydrogenated fatty acids (24. parts) obtained by hydrogenation of fish oil fatty acids and hydrogenated fat (6 parts) obtained by hydrogenated fish oil fat. The gum arabic-oil-fat solution was heated at about F. and agitated vigorously, whereupon an emulsion was obtained. Caustic soda solution (45 per cent aqueous solution, 4 parts) was added to the emulsion at 160 F., agitation being completed in 10 minutes. The mixture thus obtained was heated and agitated for 3 hours at 280 F. to complete the saponification and was substantially dehydrated (water content-01 per cent) thereafter by heating or fire-cooking to a temperature of 330 F. The grease was then allowed to cool, whereupon it solidified. The final product, hereinafter referred to as Grease I, is identified by the following characteristics, all figures being on a dry basis:

Per Cent Grease I Hydrogenated Fatty Acids 30. 3 Hydrogenated Fat 7. 3 Sodium Hydroxide 5. 7 Mineral Oil. 55. 45 l. 25

Gum Arabic Grease II Per Cent Hydrogenated Fatty Acids 30. 65 Hydrogenated Fat 7. 4 Sodium Hydroxide"- 5. 8 Mineral Oil 56.15 Gum Arabic None Grease II was prepared by direct saponification of fatty materials and mineral oil with a strong caustic solution in the proportions indicat-v ed above and thereafter was substantially dehydrated. V

One-inch cubes were cut from 1" thick grease slabs which were representative cross sections of the grease blocks .under test. The cubes were placed on an open tray and the tray was placed on a shelf in a constant temperature electric oven. The cubes were heated at 250 F. for one hour, at 300 F. for one hour, and finally at 350 F. without being removed from the oven. After each of the aforesaid heating periods, the top side of each cube was slightly pressed'down with the fiat side of a spatula to determine whether there was any deformation or slumping of the cube. In order to pass the test, the sample should show only a slight spreading at the base of. the cube and:

no free oil at the base of the cube after the third test period of 350 F. The results (average of 4 tests) of these tests are tabulated below:

Dimensions of Test Cubes Iilelrzrgaegt Per cent Grease in Base Decrease Oil at Base Before Heating After Heating Area m Helght II II II II 1.00 xtgg 1.188 x1. 182 40 13 None II I! I! I! x {8%, F 3 3;, 64 3s Considerable;

It will be apparent from the foregoing results that Grease I, which contains gum arabic, is greatly superior to Grease I in its resistance to bleeding;-- asshownby the oil extruded from the lattergrease and also in its substantially smaller degree of deformation. The improved greases of this invention are excellent lubricants for locomotive driving journals where high temperatures and pressures are encountered. They also find application as anti-friction bearing greases; for example, ball bearing and roller bearing greases. Other applications for these improved greases will be apparent to those skilled in the art.

The characterizing materials of this invention, as pointed out above, may be used in various amounts in imparting improved properties to greases. In general, the various constituents (on a dry basis) of greases contemplated herein may vary within the following limits:

, Per cent Fatty material 8 -48 Alkali 1 7 /2 Mineral oil 29 -89% Natural gum /g-15 It is to be understood that the greases of this invention may also contain other characterizing agents and fillers. For example, they may contain grease anti-oxidants, such as amines, phenols, sulfides, etc.; fillers, such as asbestos, graphite, mica, talc, etc. and lubricity improving agents, such as free fat, free fatty acids, sulfurized fats, and lead soaps.

It is to be understood, moreover, that the foregoing specific examples are but representative of the greases contemplated herein. The present invention, therefore, is not to be construed as limited thereto but is to be broadly interpreted in the light of the claims appended hereto.

This application is a continuation-in-part of co-pending application Serial Number 602,667, filed June 30, 1945, now U. S. Patent 2,241,720.

We claim:

1. A lubracting grease composition prepared from about 8.5 to about 48 per cent of a fatty material, about 1.5 to about 7.5 per cent of an alkaline material selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides, about 0.5 to about 15 per cent of a water-dispersible natural gum, and mineral oil by heating together the fatty material, mineral oil, and a water solution of the natural gum, saponifying the resulting mixture with the aforementioned alkaline material and heating at a temperature within the approximate range 250-400 F. to yield a substantially anhydrous metal base grease.

2. A lubricating grease composition prepared from about 8.5 to about 48 per cent of a fatty material, about 1.5 to about 7.5 per cent of an alkaline material selected from the group consisting of alkali metal hydroxides, and alkaline earth metal hydroxides, about 0.5 to about 15 per cent of gum arabic, and mineral oil by heating together the fatty material, mineral oil, and a water solution of gum arabic, saponifying the resultant mixture with the aforementioned alkaline material and heating at a temperature within the approximate range 250400 F. to yield a substantially anhydrous metal base grease.

3. A lubricating grease composition prepared from about 8.5 to about 48 per cent of a fatty material, about 1.5 to about 7.5 per cent of an alkali metal hydroxide, about 0.5 to about 6 per cent of awater-.d.-isperslb1e natural-gum, and mineral oil by heating together the fatty material, mineraloiland a. water solution of the natural gum, saponifying the resultant. mixture with alkali metal hydroxide and heating at a temperature within the approximate range 250-400" F. to yield a substantially anhydrous alkali metal base grease.

4. A lubricating grease composition prepared from about 8.5 to about 48 per cent of a fatty material, about 1.5. to about 7.5: per centof sodium hydroxide, about 0.5 to about 6' per cent of gum arabic, and mineral oil by heating together the fatty material, mineral oil, and a water solution of gum arabic, saponifying the resultant mixture with sodium hydroxide and heating at a temperature within the approximate range 250-400 F. to yield a substantially anhydrous sodium base grease.

5. A substantially anhydrous soda soap lubricating grease characterized by resistance to deformation and bleeding, comprising suflioient mineral oil to form said grease, a sodium soap content of from about 10 to about 55 per cent and from about 0.5 to about 15 per cent of a waterdispersible natural gum.

6. A substantially anhydrous soda soap lubrieating grease characterized by resistance to deformation and bleeding, comprising suificient mineral oil to form said grease, a sodium soap content of from about 10 to about 55 per cent and from about 0.5 to about 6 per cent of gum arabic.

7. A substantially anhydrous lubricant selected from the group consisting of alkali metal base greases and alkaline earth metal base greases characterized by resistance to deformation and bleeding, comprising sufficient mineral oil to form a grease, a soap content of from about 10 to about 55 per cent and from about 0.5 to about 15 per cent of a water-dispersible natural gum.

.8. A substantially anhydrous lubricant selected from the group consisting of alkali metal base greases and alkaline earth metal base greases characterized by resistance to deformation and bleeding, comprising sufficient mineral oil to form a grease, a soap content of from about 10 to about 55 per cent and from about 0.5 to about 15 per cent of gum arabic.

9. A lubricating grease composition characterized by resistance to deformation and bleeding, comprising the reaction products of the following ingredients in the indicated proportions:

I Per cent Fatty material 8 /g-48 Alkali 1 7 Mineral oil 29 89 'Water-dispersible natural gum /g-15 and prepared by heating together the aforesaid ingredients to form an alkali soap mixture which is thereafter dehydrated at a temperature of 250-400 F., yielding a substantially anhydrous metal base grease.

10. A lubricating grease composition characterizedby resistance to deformation and bleedin comprising the reaction products of the following ingredients in "theindicated proportions:

, Per cent Hydrogenated fatty acids 30.3 Hydrogenated fat 7.3 Sodium hydroxide 5.7 Mineral oil 55.4 Gum arabic 1.25

and prepared by heating together the aforesaid ingredients to form a soda soap mixture which is thereafter dehydrated at a temperature of 250-400 F., yielding a substantially anhydrous soda base grease.

TI-LEODORE G. ROEHNER. GEORGE W. MURRAY.

REFERENCES CITED 10 The following references are of record in the file of this patent:

Number Number UNITED STATES PATENTS Name Date Cook et a1. Apr. 21, 1874 Thomsen et a1 Jan. 24, 1933 Brunstrum Feb. 15, 1938 Kaufman et a1 Dec. 1, 1942 Dew Apr. 4, 1944 FOREIGN PATENTS Country 7 Date Sweden Oct. 4, 1919 

